[Amps] triode vs tetrode

[Jim Thomson]

Date: Mon, 5 Dec 2016 18:06:33 -0600
From: Joe <nss at mwt.net>
To: "amps at contesting.com" <amps at contesting.com>
Subject: [Amps] triode vs tetrode

OK like a 3-500Z, 3CX bla bla bla etc. are triodes, plate, grid, and 
well filament.

Most of these tubes run grounded grid correct? so the grid is simply 
grounded.

Now the 4CX bla bla bla is plate, screen, grid, and whatever filament etc.

What would happen if you simply wired it up like  triode in grounded 
grid. ground both the screen and the grid,  has anyone ever tried that?

Joe WB9SBD

##  That works good on tubes like the 4CX-3000 / 5000 / 10,000 / 15,000 
Done on all the time.  Requires more drive than a true Triode, and IMD is
a bit less. 

##  it also works on 4-125 / 4-250 / 4-400 A/B/C . 

##  This is yet another reason to directly bond the grids to chassis on any
SB-220 / L4B /  Henry Amp  /  TL-922.   Then you can shovel
a  4-400 A  / B  / C   directly into any 3-500Z amp, and it will run just fine,
albeit with less idle current, and slightly higher drive requirements. 

##  On tubes like the  4CX-1000 / 1500,   the grid dissipation is non existent.
0 watts on the 1000..and only   1 watt on the 1500.   In those cases, the
config used is called... super cathode driven.  The control grid is bonded to the
cathode.  The screen grid is  bonded to the chassis.   But higher drive is required.
A  4CX-1000  will require 160 w of drive to get 1200 w pep out.  I know 2 x VE7
folks  who use that config, and it works just fine with no imd issues.  

Jim  VE7RF